The present invention relates to an automatic sawmill and particularly to automatic sawmill apparatus for removing an irregular edge from a cant or board.
In automatic sawmill operation, a maximum recovery in board feet of lumber from incoming logs is desired, as well as high volume capacity for handling and cutting the maximum lumber in a given period of time. One problem associated with automatic sawmill operation is removal of the irregular lateral edge on a plank or a cant. For example, it is necessary to remove the wane edge on a plank or cant, i.e. the rounded or non-squared edge resulting when such plank or cant is sawn lengthways from a round log. The wane must be removed, within certain tolerance restrictions, before the plank or cant is processed into dimensioned lumber. Of course, the wane can be sawn from the cant after visual inspection or measurements by operating personnel, but this can be unnecessarily expensive and time consuming. Merely trimming all cants within certain dimensions to remove all possible wane areas would be unduly wasteful.
Automatic detectors for measuring uneven edges or wanes are known, but implementing the measurements derived therefrom for removing the undesired irregular edge or wane may be somewhat inaccurate. After detection, the plank or cant is frequently moved some considerable distance before sawing, and the correct orientation of the plank or cant relative to a saw used for removing the irregular edge can be difficult to maintain. Thus, in the course of measurement and removing of the undesired edge, the cooperation of two conveyor systems is often required, i.e., one to orient the cant for correct sawing, and a second conveyor, usually operated in perpendicular relation to the first, for moving the cant lengthways through a stationary saw. Cumulative errors can result requiring in effect the removal of more of the edge than would really be necessary, or resulting in a slowdown in the handling capacity of the apparatus for the sake of greater accuracy.